The actylcholine receptor transduces the binding of acetylcholine into an increase in the permeability of the postsynaptic membrane to cations. The goal of this proposal is to correlate the structure of this protein with its function. The distribution of the receptor through the postsynaptic membrane will be investigated by the analysis of the neutron scattering of oriented receptor-rich membranes. The exposure on the intracellular side of the membrane of segments of the four different kinds of subunits that constitute the receptor will be investigated by immunocytochemical and chemical means in open membrane fragments. The relative positions of the subunits will be examined by electron microscopy of negatively stained receptor. The subunits will be identified by their known pattern of cross-linking and by specific identifiable tags. The location of local anesthetic binding sites and of sites associated with the cation channel will be sought by affinity labeling and peptide mapping techniques. By these approaches, we will be able to assign functional roles to the various subunits of the receptor.